This invention relates to an ultrasonic type blood flow amount measuring apparatus for measuring blood flowing (ml/sec) through a region of interest of a human subject, through the utilization of an ultrasonic Doppler effect.
In a conventional blood flow amount measuring apparatus, utilizing an ultrasonic Doppler effect, an ultrasonic transducer emits an ultrasonic beam of a frequency, fo, to a blood flow in, for example, the blood vessel, in which case the ultrasonic beam emitted is echoed, to be exact, from the blood cell in blood flowing through the blood vessel. At this time the frequency of the echo signal varies in accordance with a blood flow speed due to a Doppler effect resulting from a relative motion between the ultrasonic beam and the bloodstream. With fd representing the Doppler shift frequency of the echo signal of the echo wave at this time a relation between fd and fo as given below holds: ##EQU1##
The angle .theta. is an angle between the emission direction of the ultrasonic wave and the direction of the bloodstream. The speed v of the flow of blood is calculated from the aforementioned equation by measuring the angle .theta. and thus an amount Q (ml/sec) of blood flow is calculated by multiplying the blood flow velocity v and inner section area S of the blood vessel.
In the conventional blood flow amount measuring apparatus, it is necessary to measure the angle .theta. between the direction in which the ultrasonic beam is emitted and the direction in which the blood flows. This angle should be measured, while observing a blood vessel section image on a monitor screen, and the measurement of that angle .theta. is very difficult, failing to measure an exact amount of blood flowing through the heart.